1. Field of the Invention
This invention relates generally to a shock-resistant support structure for use in a portable laser scanning head in a laser scanning system for reading bar code symbols and, more particularly, to a support structure, preferably comprised of a pair of readily detachably connected support elements, for readily removably supportably mounting thereon a laser tube component, an optical component and a scanning component, as well as for properly positioning the components after their mounting and/or for properly re-positioning the components after their removal, to facilitate component assembly and disassembly.
2. Description of the Prior Art
In the field of laser scanning systems for reading bar code symbols, it has heretofore been proposed to arrange together various components, for example, a laser tube component for generating a laser light beam, an optical component for optically modifying and directing the laser light beam along a light path, and a scanning component for scanning the laser light beam over a field of view across a bar code symbol to be read.
For example, as shown in a 1976 advertising flyer entitled "VERIFIER 315" of UPC Film Masters, Inc., a portable laser scanning head was advertised as having at least a laser tube component, an optical component and a scanning component mounted within a hand-held housing. An article entitled "NEEDED: BETTER QUALITY CONTROL FOR UPC", by Harrison and Swartz, which appeared at pp. 61-63 in the October 1976 edition of Food Engineering, also described the arrangement of the aforementioned components relative to one another. An article reprint of the VERIFIER 315 instrument also appeared at p. 50 of Packaging in 1976. The VERIFIER 315 instrument was sold in a version wherein the optical and scanning components were mounted within the laser scanning head, and wherein the laser tube component was plugged into the rear end of the head.
In another prior art proposal, U.S. Pat. No. 4,251,798 disclosed the interior mounting of the laser tube component, the optical component and the scanning component on both sides of a planar center plate or optical bench which subdivided the interior of a laser scanning head. The laser tube component was supported underneath the center plate and was essentially strapped in place therebelow.
U.S. Pat. No. 4,387,297 disclosed the mounting of the aforementioned laser tube, optical and scanning components on a support plate or motherboard within a laser scanning head wherein rubber bumpers were used to make the plate-mounted components shock resistant. Again, the laser tube component was strapped in place on the support plate.
In another prior art proposal, U.S. Pat. No. 4,409,470 disclosed the shock-resistant mounting of the laser tube component, not with the aid of straps, but by its close-fitting reception into a cylindrical support sleeve. U.S. Pat. No. 4,409,470 also disclosed the shock-resistant mounting of the optical and the scanning components on a separate optical bench or generally block-shaped support. The aforementioned support sleeve was connected to the optical bench by being snugly received in a bore formed in the bench. In practice, an adhesive was typically used to fixedly secure the support sleeve in the bore of the bench. In addition, an adhesive was also customarily used, in practice, to fixedly secure the various optical parts of the optical component to the bench. For example, a concave lens part which was positioned adjacent the output end of the laser tube component was glued inside another bore formed in the bench, and a pair of light-reflecting mirror parts was also respectively glued in place on a pair of inclined surfaces of the bench. A convex lens part was adjustably mounted on the bench by means of a set screw.
Although the above-described prior art supporting structures generally served their intended support purpose, they did not prove to be altogether satisfactory during component assembly and/or disassembly, particularly during field maintenance. Thus, it was somewhat time-consuming and inconvenient for the assembler to be compelled to assemble and/or disassemble the aforementioned components on opposite sides of a center plate, and to strap and/or unstrap the laser tube component in its proper position on the support plate. Although it was much more convenient, as taught by U.S. Pat. No. 4,409,470, to slide the laser tube component into and out of the aforementioned cylindrical support sleeve for easier assembly and replaceability, as opposed to the earlier techniques of strapping and unstrapping the laser tube component to a support plate, the glueing of the support sleeve in place in its respectively associated bore in the bench was a painstaking and a time-consuming operation. If this glueing procedure was eliminated or was poorly done during assembly, then the possibility arose, during careless or rough handling of the laser scanning head, that the support sleeve would either become detached from the bench or slightly shift relative thereto, thereby causing an optical misalignment problem.
In addition, it was painstaking and very time-consuming to glue the aforementioned pair of mirror parts in place on the inclined surfaces of the bench. In the event of any mishandling of the laser scanning head, the possibility arose that the mirror parts could either shift or perhaps even fall off the bench, thereby rendering the laser scanning head inoperative. Of course, when the glueing procedures were properly performed, then the resulting fixed connections were somewhat difficult to undo. Also, it was laborious to set the proper position of the convex lens part by adjusting the set screw. It would have been difficult and time-consuming, particularly during field replacement and maintenance, to unglue and/or remove the support sleeve and/or mirror parts and/or lenses from their essentially permanently fixed connections.